Automated Driving Systems (ADS) continue to be a hot topic in the ROS community, but what comes next? The answer is cooperation and coordination between ADS systems and infrastructure. This talk will describe how the CARMA Program uses existing technologies to enable Cooperative Driving Automation (CDA). We will discuss how CARMA implemented its vehicle-to-everything (V2X) communications stack in ROS and built upon Autoware.ai to enable CDA operations such as platooning, and dynamic route updates.